Reversibly Switching Bilayer Permeability and Release Modules of Photochromic Polymersomes Stabilized by Cooperative Noncovalent Interactions

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• 作者：Xiaorui Wang ; Jinming Hu ; Guhuan Liu ; Jie Tian ; Huijuan Wang ; Ming Gong ; Shiyong Liu
• 刊名：Journal of the American Chemical Society
• 出版年：2015
• 出版时间：December 9, 2015
• 年：2015
• 卷：137
• 期：48
• 页码：15262-15275
• 全文大小：856K
• ISSN：1520-5126

文摘

We report on the fabrication of photochromic polymersomes exhibiting photoswitchable and reversible bilayer permeability from newly designed poly(ethylene oxide)-b-PSPA (PEO-b-PSPA) diblock copolymers, where SPA is spiropyran (SP)-based monomer containing a unique carbamate linkage. Upon self-assembling into polymersomes, SP moieties within vesicle bilayers undergo reversible phototriggered isomerization between hydrophobic spiropyran (SP, 位₂ > 450 nm irradiation) and zwitterionic merocyanine (MC, 位₁ < 420 nm irradiation) states. For both SP and MC polymersomes, their microstructures are stabilized by multiple cooperative noncovalent interactions including hydrophobic, hydrogen bonding, 蟺鈥撓€ stacking, and paired electrostatic (zwitterionic) interactions, with the latter two types being exclusive for MC polymersomes. Control experiments using analogous block copolymers of hydrophobic SP monomer with a carbonate linkage (SPO) and conventional spiropyran methacrylate monomer (SPMA) containing a single ester functionality were then conducted, revealing that carbamate-incurred hydrogen bonding interactions in PEO-b-PSPA are crucial for polymersome stabilization in the zwitterionic MC state. Moreover, reversible phototriggered SP-to-MC polymersome transition is accompanied by membrane polarity and permeability switching from being nonimpermeable to selectively permeable toward noncharged, charged, and zwitterionic small molecule species below critical molar masses. Intriguingly, UV-actuated MC polymersomes possess two types of release modules: (1) sustained release upon short UV irradiation duration by taking advantage of the unexpectedly slow spontaneous MC-to-SP transition kinetics (t_1/2 > 20 h) under dark conditions; (2) on-demand and switchable release under alternated UV鈥搗is light irradiation. We further demonstrate photoswitchable spatiotemporal release of 4鈥?6-diamidino-2-phenylindole (DAPI, cell nuclei-staining dye) within living HeLa cells.